I don't see anything unChristian about attacking Robertson. In fact, I think it's the duty of Christians everywhere to stand up and condemn that kind of hateful nonsense. If we don't make it clear that Pat Robertson does not represent the rest of us, we'll get more and more people seeing his hatred as the norm for people of faith.
Part of me hopes the Rapture actually happens so that someone can take a photo of the look of utter shock on Pat Robertson's face when he isn't taken.